1. Technical Field
The present invention relates in general to absorbent structures for electronic equipment and methods of preventing the encroachment of liquids into the electronic circuitry of devices. More particularly, the present invention relates to the use of a hydrogel-forming compounds such as salts of polyacrylate encased in a pre-formed structure that fits within such articles as computer keyboards in order to prevent the encroachment of liquids into the electronic circuitry of the keyboard.
2. Description of the Related Art
In typical usage, various types of electronic devices such as computers, cell phones, remote controls, PDAs, radios, and other electronic articles require human contact and are thus exposed to possible liquid spills and encroachment by rain, and/or water laden vapor including high humidity and fogs, etc. The cost of replacing electronic circuitry due to liquid compromise, which typically leads to shorts in the system, the failure of keyboard elements, etc, is great when considering that computer keyboards are so prevalent, and their use along with our daily activities, such as in cell phones and laptop computers, is so commonplace. Thus, there has been great interest in a means of protecting such electronic devices from liquid spills.
Most attempts to block liquid spills in electronic devices involve the use of an impermeable liquid barrier that diverts the flow of liquids that should fall into the crevices of a keypad or keyboard. The impermeable barriers in the prior art, such as disclosed in U.S. Pat. No. 5,681,122 involve the use of a tray having walls and a spillway that is located below the external facie of the computer keyboard but above the electronic equipment, the tray having formations to allow the keys of the keyboard to float through. Spills would then fall into the spaces between the facie and keys and into the tray, to be collected at the spillway. Other means of protecting electronic devices from liquid spills include such means as disclosed in U.S. Pat. No. 5,491,478, wherein a unitary molded seal membrane is sealed over the top of keys on a cell phone or keyboard keypad, thus directly blocking the flow of spills. A third protection means is a thermal heat seal of a laminated PVC membrane with the electronic traces contained within the seal. This, however, offers only limited water resistance, and breaks down over time.
There are numerous problems with the prior art. The use of such means as a tray requires that the liquid fall downwardly directly into the keypad or keyboard. This does not take into account the encroachment of moisture due to rain, fog, or spills that are substantially non-vertical. The problem with the membrane-type of barrier is that they prevent free and unhindered use of the keypad or keyboard. Further, these membranes typically wear over time and become translucent or even opaque, thus requiring replacement. Since these articles must be fastened securely around the keypad or keyboard, it is not convenient for a typical user to easily replace them. As mentioned above, sealed plastic laminates offer only minimal protection and requires thin silver traces, which is subject to corrosion, fatigue, and cracking.
There is thus a need for an improved method of protecting the electronic circuitry in devices such as cell phones, ATM machine keypads, laptop computer keypads, remote controls, PDAs, radios, and other devices where the threat of liquid spill or moisture exposure may be present. This need is heightened by the fact that electronic equipment such as laptop computers, cell phones, phones in phone booths, marine electronic equipment, and other electronic equipment finds more widespread outdoor use.
It is therefore one object of the present invention to provide an improved means of protecting electronic circuitry in electronic devices from liquid spills and moisture.
It is another object of the present invention to provide an absorbent structure within electronic devices that can reversibly absorb liquids or can be easily and conveniently changed out.
It is yet another object of the present invention to provide a means of protecting keypads and keyboards functionally associated with electronic devices from rain, moisture, fogs, mists, condensate, and other non-vertical spills and liquid encroachment.
The foregoing are achieved as is now described, wherein a method of reversibly absorbing aqueous solution penetrations into electronic devices having a body and circuitry is herein disclosed and claimed. The method comprises providing an absorbent structure having a defined thickness, the structure comprising a water-permeable top sheet, a hydrogel-forming core, and a back sheet. The back sheet may be either water-permeable or water-impermeable. The defined thickness is between about 0.1 mm and 7 mm, and preferably between about 0.5 mm and 5 mm. The absorbent structure is further characterized by having formations that allow for access to and penetration of electronic and mechanical elements. For example, the formations and shape of the structure would allow the unitary structure to fit within and around a typical computer keyboard between the external facie and electronic circuitry to be protected.
The absorbent structure is placed within the electronic device such that the top sheet portion of the structure faces away from electronic circuitry to be protected, although other embodiments may entail an absorbent structure having two water-permeable layers surrounding the hydrogel core. Further, adequate expansion volume is provided between the structure and the electronic device body when placed within the device.
The hydrogel-forming core can comprise one hydrogel forming compound such as sodium polyacrylate, or a mixture of compounds and other cross-linking agents. The top sheet is typically made from water-permeable polyethylene or cotton/paper material, and the backsheet is made from water-impermeable polyethylene or polyolefin material.
The above as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description.